feat: made BaseNode.parent non-optional

[JoshuaKGoldberg]

BREAKING CHANGE: changes the AST types in a non-backwards compatible way.

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PR Checklist

• [x] Addresses an existing open issue: fixes #1417
• [x] That issue was marked as accepting prs
• [x] Steps in CONTRIBUTING.md were taken

Overview

Doesn't quite make BaseNode's parent property generic (a good next step?), but does make Program's property parent?: never.

I removed all checks like /if \(\w+\.parent/, /!\w+\.parent/, and /\w+\.parent ((&&)|(\|\|))/, then added back any that caused type checking complaints. Those were mostly from places that recursively went up the AST via node.parent.

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[typescript-eslint[bot]]

Thanks for the PR, @JoshuaKGoldberg!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[codecov[bot]]

Codecov Report

Merging #5252 (3d65e74) into v6 (9851338) will increase coverage by 0.03%. The diff coverage is 97.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##               v6    #5252      +/-   ##
==========================================
+ Coverage   91.64%   91.67%   +0.03%     
==========================================
  Files         358      358              
  Lines       12237    12232       -5     
  Branches     3591     3585       -6     
==========================================
  Hits        11214    11214              
+ Misses        721      719       -2     
+ Partials      302      299       -3     

Flag	Coverage Δ
unittest	91.67% <97.50%> (+0.03%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...int-plugin/src/rules/consistent-type-assertions.ts	88.88% <ø> (ø)
packages/eslint-plugin/src/rules/indent.ts	92.85% <ø> (ø)
...ackages/eslint-plugin/src/rules/no-explicit-any.ts	96.42% <ø> (ø)
packages/eslint-plugin/src/rules/no-redeclare.ts	91.89% <ø> (ø)
...plugin/src/rules/no-redundant-type-constituents.ts	93.89% <ø> (ø)
.../eslint-plugin/src/rules/no-useless-constructor.ts	94.73% <ø> (ø)
...ackages/eslint-plugin/src/rules/prefer-as-const.ts	100.00% <ø> (ø)
...ckages/scope-manager/src/referencer/VisitorBase.ts	88.23% <50.00%> (ø)
packages/eslint-plugin/src/rules/array-type.ts	97.14% <100.00%> (ø)
...lugin/src/rules/consistent-generic-constructors.ts	94.87% <100.00%> (ø)
... and 32 more